9.37.3 Assembler Directives

The RX version of as has the following specific
assembler directives:

.3byte

Inserts a 3-byte value into the output file at the current location.

.fetchalign

If the next opcode following this directive spans a fetch line
boundary (8 byte boundary), the opcode is aligned to that boundary.
If the next opcode does not span a fetch line, this directive has no
effect. Note that one or more labels may be between this directive
and the opcode; those labels are aligned as well. Any inserted bytes
due to alignment will form a NOP opcode.